x86/mce-inject: Reset injection struct after injection

[ Upstream commit 7401a633c34adc7aefd3edfec60074cb0475a3e8 ]

Clear the MCE struct which is used for collecting the injection details
after injection.

Also, populate it with more details from the machine.

Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20180905081954.10391-1-bp@alien8.de


Signed-off-by: Sasha Levin <sashal@kernel.org>